[Spatial difference of microbial community structure and enzyme activity in constructed wetlands receiving wastewater...

The microbial community structure and enzyme activity were investigated in the three-stage wavy subsurface constructed wetland (W-SFCW) receiving wastewater containing heavy metals (Cr, Cu and Ni). Colony forming units (CFU) abundance of microbes was calculated by using plate culture. The microbial community structure was investigated by using PCR-DGGE and sequencing. Enzyme activity was detected by using colorimetry. The results showed that the CFU of bacteria ranged from (4.10 +/- 0.72) x 10(6) to (1.61 +/- 0.10) x 10(7), fungi ranged from (7.21 +/- 1.60) x 10(4) to (1.29 +/- 0.02) x 10(5) and actinomycetes ranged from (1.41 +/- 0.27) x 10(6) to (3.38 +/- 0.11) x 10(6). All of 8 bands retrieved from DGGE gels were unique 16S rRNA or 18S rRNA sequences and revealed that the microbial community structures had changed spatially. Maximum urease [(0.67 +/- 0.2) mg/(g x 24 h)], invertase [(40.15 +/- 0.14) mg/(g x 24 h)] and alkaline phosphatase [(1.03 +/- 0.16) mg/(g x 2 h)] activities were at first stage, third stage and first stage, respectively. A negative correlation between fungi CFU abundance and the total content of Cr, available Cr content and activation rate of Cr was detected, a negative correlation was also found between the invertase activity and total Cu and Ni contents and the Ni activation rate.